Field
This disclosure is generally related to the field of data storage. More specifically, this disclosure is related to a method and system for rearranging a write operation in a shingled magnetic recording device for improved system performance.
Related Art
The proliferation of the Internet and e-commerce continues to create a vast amount of digital content. Various storage systems have been created to access and store such digital content. In a standard storage system, a server may store data in a non-volatile memory, such as shingled magnetic recording (SMR). While conventional hard disk drives record data by writing non-overlapping magnetic tracks parallel to each other (perpendicular recording), an SMR device writes new tracks that overlap part of the previously written magnetic track. The tracks partially overlap similar to roof “shingles.” A narrower track width can result in a higher track density and an increased storage capacity. Furthermore, SMR can address physical limitations which prevent recording magnetic heads from having the same width as reading heads, leaving recording heads wider.
However, while SMR addresses some physical limitations, SMR introduces others. The overlapping-tracks architecture may create efficiencies in performing a write operation. While writing or appending data to SMR in a sequential manner may not affect neighboring or overlapping tracks, writing data randomly to a portion of a band which already stores data may result in a delay. This delay may occur because writing data to one track can require re-writing data to the neighboring or overlapping tracks. That is, the system must read out the entire band, modify the specific portion, and write back the entire modified band. In the case where the update is small in comparison so the size of the band (e.g., a 4 KB update sector in comparison to a 128 MB or a 256 MB sequential write block or band), the write amplification may result in a high latency, which can decrease the efficiency of a storage system.